(CNN) - As Muhammad Ali stood up and slowly raised his right hand to greet friends in celebration of his 70th birthday at the Muhammad Ali Center in Louisville, Kentucky, last weekend his voice was silent. But the three-time heavyweight champion winked, smiled and engaged with those who came to support him.

His 70th birthday on Tuesday represents a poignant milestone for a man once known for his speed, wit, grace and fearlessness.

“My father is feeling very blessed and proud to be turning 70,” Ali’s daughter, Hana Ali, said.

Fifty years ago, Ali proclaimed himself “The Greatest” and millions of boxing fans around the world agreed. His charisma and courage made him the most famous figure on the planet.

Ali’s legacy began in 1942, when he was born Cassius Marcellus Clay Jr. in Louisville, Kentucky, during an ugly era of racial segregation in America. At age 12, Ali's world changed forever when a white police officer introduced him to boxing. According to Ali biographer Howard Bingham, the young Clay had ridden his new bicycle to a carnival for free popcorn and candy. After discovering it missing, Clay vowed to beat up the thief. While reporting the theft, police officer and volunteer boxing coach Joe Martin persuaded Ali to learn to box. The sport became an outlet for his rage and offered the young fighter an opportunity to develop his remarkable talent.

Ali’s international fame emerged a few months after his 18th birthday, when he represented the United States at the 1960 Olympic Games in Rome and won a gold medal. While Ali returned to Louisville with a hero’s welcome, whites still refused to serve him because of Jim Crow laws and racial bigotry.

At 18, Ali turned pro and four years later, he stunned the boxing world by defeating a fighter most experts thought was invincible - heavyweight champion Sonny Liston.

The 1960s were glory days for Ali, but the civil rights era became a controversial and polarizing period in his life. He renounced his given name of Cassius Clay and joined the black separatist Nation of Islam.

“Ali was a child of the South and understood racial segregation, he watched as black people were beaten, bitten by dogs and lynched and all of that had an impact on him,” said Harry Edwards, a sports sociologist and University of California, Berkeley professor emeritus.

Outside the ring, Ali often found himself at the center of civil rights protests.

“Self determination was a powerful image at that time and instead of striving to share space with people who hated blacks, Ali took the position that “We as black men are able to stand on our own feet, develop our own institutions and be men,” Edwards said. “The slogan that 'I am black and I am proud' had a tremendous appeal to him and it had a generational change on the image and disposition of the black athlete."

In 1967, almost as quickly as Ali had arrived, his heavyweight title was gone - revoked after he claimed conscientious objector status and refused to serve in the Vietnam War. At the peak boxing age of 26, also Ali gave up tens of millions of dollars in endorsements and faced five years in prison, all in defiance of a war that he called “despicable and unjust.”

Ali would fight his case all the way to the U.S. Supreme court, where his conviction was overturned on a technicality in 1971.

“When Ali put everything he achieved on the line in deference to his religion and political principles that got attention around the world,” said Edwards. “People eventually came to believe Ali was sincere and over time there developed a tremendous degree of unquestioned integrity about him,” said Edwards.

On March 8, 1971, the world learned that even heroes have off days. Ali was barely back in the ring when his undefeated professional record came to an end. He lost to Joe Frazier in a 1971 match dubbed "The fight of the century." It was the first of three fights with "Smokin’ Joe.” In 1975, Ali faced Frazier a third time in the famous “Thrilla in Manila.” It ended with a 14th round knockout, a triumph by Ali.

Perhaps his greatest athletic comeback was in central Africa, where Ali knocked out the heavily favored young champion George Foreman in the fight known as the “Rumble in the Jungle.” In 1978, Ali would recapture the heavyweight title for a record third time, defeating Leon Spinks.

His last professional fight in 1981 marked the beginning of another battle, what Ali described as his toughest: the Parkinson's disease diagnosis he received three years later.

After two decades of redefining the heavyweight division, Ali’s lifetime record: 56 victories, just five defeats.

According to Hana Ali, the heavyweight champion was never content with simply winning titles.

"I've always wanted to be more than just a boxer,” she quoted him as saying. “More than just the three-time heavyweight champion. I wanted to use my fame and this face that everyone knows so well, to help uplift and inspire people around the world. I've made my share of mistakes along the way but if I have changed even one life for the better, I haven't lived in vain,” quoting her father.

As his condition worsened, Ali continued to serve as a mediator in world conflicts. In 1990, before the first Gulf war, Ali personally visited former Iraqi leader Saddam Hussein to secure the release of 14 U.S. citizens held captive and used as human shields.

“The fact that he was a serious and dedicated Muslim devoted to put everything on the line including his life, in a culture like Iraq, if Ali comes in and says let these people go, even a monster such as Hussein could probably at some level be moved by his humanity,” historian Edwards said.

“As a Muslim, my father’s spirituality is constantly growing,” Hana Ali said. “When he speaks about religion these days, my dad’s closing remark is always the same, 'There is only one true religion and that is the religion of the heart because we are all here to improve the human condition.'"

While Parkinson’s disease took its toll, Ali didn't retreat from public life. In a poignant moment in modern sports, Ali ignited the Olympic flame in 1996 to begin the summer games in Atlanta. With more than 3.5 billion viewers world-wide, the man once known as the most famous person on Earth slowly ascended the stadium steps, his hands trembling but never wavering - Ali at his best, again.

While Ali has been robbed of physical traits he once treasured - fluid, elegant moves - his commitment to human rights hasn't wavered.

“He was bigger than just the greatest boxer he was a transcendent iconic figure who impacted and influenced the character of a generation,” Edwards said.

As Ali turns 70, few would argue that Ali needed the crowds as much as they at one time needed him - not for personal approval, but because each saw the best of Ali’s humanity in themselves.

Hana Ali said: “My father said to me the other day, 'Belief in yourself is like a staircase, as long as we are here on earth we must continue to climb.’”

Muhammed Ali said "A man who sees the world the same at 40 as he did when 20, has wasted 20 years" I was serving in VietNam when Ali refused to go. I despised him, and most of his race at that time. Today I admire the man for standing for his own beliefs, and my prejudice is gone. You need to grow washington. Also, Frazier was a great boxer, but he was not the "Greatest"

Muhammad Ali is the REAL-MAN pattern, that all the hateful caucasian male's wish they could be. Because you, caucasian male, could NEVER stand up against a racist superpower, and still be standing after all the low-blows, and pits that your people dug for Ali to fall in. You-yourselves, racist-caucasian males, fell in those pit's! And you will continue to fall as long as you continue to be racist, and do your evil against the good people of color.

Let me guess, you were also never denied access to public facilities, forced to sit in a specifc bus seat or other illegal activities. It is because of Ali that millions & millions of people around the world have the right to say NO to injust in all of it's evil forms. That 1 man standing up for his beliefs in a country that would not treat him as an equal was far, far more important than any military service he may have had.

My father and most of the white men in my father's era disliked Ali because they disliked any notion of black success. But for me, growing up in the 60's and 70's Ali really was the greatest, and he was the man that showed me clearly that "black is beautiful." Happy birthday to you!

Why should a man fight for a country that wouldn't even respect him after he won a medal in the name of that country.. Fight in a war that he doesn't believe in why? He couldn't eat along side white people and you wanted him to go to war right.....

Muhamed Ali is the greatest political warrior and boxing supremo of all time. The Parkinson disease ailment needs to be investigated. He is a great American irrespective of what his detractors may say.

I've known Ali since 1988. My children call him Uncle Ali. He is the single bravest, kindest, most generous soul any of us could wish to meet. Seeing him in person, almost everyone recognizes he's in the presence of a great man. His Parkinson's has made him the world's sick, nearly infirm grandfather. Nearly every time I've been with him, I've watched grown men weep when they meet him. I've watched him tug children to his chest who are dying from imminently contagious diseases and kiss them and hold them as if he were their father. I can't imagine a better, more meaningful mythology for The Greatest of All Times than to regard him as a sick favorite family member to us all. Happy birthday, Champ.

I got to watch Mr Ali in Conn. years ago when he did a 5 round exhibitionism . He was over weight and slow. But I respect him for his stance on the war. Remember all you nay Sayers when you went off to fight you also went off to fight for the RIGHT to CHOOSE. You may not like the persons choice but that is the down side of freedom of speech. Just saying ..Happy Birthday and may you fly like a butterfly and sting like a bee!

desert voice (troubledgoodangel or Nathanael or Bohdan or Voiceinthedesert)

I respect Ali for trying to be the best human being he can be. But his Moslem religion does not resonate with me as a religion best suited "for better mankind! I do not blame Ali. I blame those who got him into this mess. And I would like to ask Ali on the record: Does he still believe that Islam is a peaceful religion?

seems you have no idea of the times and troubles in those days,what would you have done back then in a segregated country.the black muslim movement back then was a place a black man or woman could feel part of somrthing

I was going to reply in anger to all you idiotic trolls, but then decided to take a lesson I learned from Muhammad Ali and just ignore. You all are not worth the effort. Ali was my hero back in the 60's and still is today.

Hate to say it. But Dave is right. He's nothing but a draft dodger and used the bounty of this wonderful country to have a professional boxing career that made him millions.

When I was growing up, I liked him in the 70's. Then I realized his politics and his anti-USA rants. I then say "To hell with you Ali, I'm glad the good lord Jesus has taken away your sassy stupid mouth"

Muslims are garbage the worse kind of people they have no place in america, they already took over most of michigan. They truly make me sick, their ideas are beyond stupid. Being muslim is close to being a nazi.

@Dave today We cheer on the People in the middle east standing up against their country's elite when they feel their governments are wrong , in fact we send bombs in to help their "cause" so when an American stands up to something that is wrong in America, you can't call him by his real name?

Thomas Jefferson came to America and brought with him is copy of the Quran, Muslims are as much American as you "Dave". start showing some respect to your own Nation.

First off, his name is not Muhammad Ali it is Cassius Clay, he changed his name to avoid the draft in the 70's. And he should never have been allowed to box in the U.S.A ever again because it. Worship this ass all you want but we still know what the truth is, Cassius Clay is a draft dodger.

Hey Dave, I went to college to avoid the draft, am I a draft dodger too? Ali was and always will be one of the most prolific boxers ever. The heavyweight division has never been as good or as profitable since Ali retired. To me he's a great man, and a great athlete. What are your accomplishments?

If you can dodge the draft and become President, you can dodge the draft and be a boxer. Quit your whining, racists. Millions of Americans found a way not to go to the Vietnam war, because they had a consciences. Maybe you should get one too.

I have long been a fan of Muhammad Ali. I admire him as a champion, but I respect him as a man of principle and character. I grew up in the 60s and I didn't find out about his politics until later. The best steel is forged in the hottest fire.

I met him in the south side of Chicago while doing some work at a Zayre store. He was in his Winnebago campaigning for Jesse Jackson's presidential bid and also for his own ministry. Run Jesse Run! That was in the late 80's. After his autograph and hand shake, he asked what a white boy was doing in this part of town? "Just doing a job, but you won't see me after dark," was my answer. He laughed. His motor reflexes and shaking led me to believe he was older than 80 back then. A gentle giant from my experience.

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